What's nice about the new folder structure is that no templates sit in core. So the page, article, block, nav templates all sit in the themes folder to customisation is not limited. This will allow the developers to theme font icons or use a sprite sheet and even a combination.
With regards to font icons and IE7. Support is there but the way font icons are implemented is through using the css 'content' attribute. This hides it away from screen readers. IE7 I believe, actually puts the font symbol into the element so it's picked up in a screen reader. Also windows phones don't support @fontface or custom fonts. I know when we research the figure was around 15% usage in the UK.
This is probably something that would go in to the readme.txt or info file each theme will have.